Incubated for 24 h with increasing concentrations CCI-779 Temsirolimus of MXN and CDV either separately or in combination. Synergy was determined using the MacSynergy鈩?II software. Mitoxantrone showed significant synergistic activity in combination with CDV, with a peak volume of 324.06 lM2%. In vitro peak volumes above 100 lM2% are considered to be highly predictive of in vivo efficacy. To determine if the significant synergistic activity against CPXV observed between MXN and CDV in tissue culture extended to in vivo models, MXN and CDV were tested in an established model of CDV synergy. BALB/c mice challenged intranasally with CXPV were treated 1 day post challenge with MXN and CDV. Log rank tests were performed to compare the survival times between different treatment groups. Comparisons of the CDV only groups were relative to the mock treated animals. Within CDV groups, comparisons of CDV MXN were made relative to those receiving CDV only. Mitoxantrone exhibited a minimal effect on survival when used alone against CPXV. The use of MXN in combination with CDV had a minimal effect on survival relative to the use of CDV alone. Fewer animals survived treatment with 100 mg/kg CDV and 0.25 or 0.5 mg/kg MXN compared to that dose of CDV alone. This trend was suggestive of MXN in combination with high doses of CDV being detrimental to animal survival, although the data did not meet our criteria for significance. Overall, these data show that MXN has minimal in vivo synergistic activity in combination with CDV against CPXV in BALB/c mice. In summary, we evaluated MXN, an anthracycline derivate that had previously been characterized as an in vitro inhibitor of VACV infection, for activity against CPXV and MPXV.
Both viruses were sensitive to MXN in vitro, and MXN increased the MDD of C57Bl/6 mice infected with a lethal dose of CPXV. An in vitro screen for synergy between MXN and CDV indicated that MXN may be more effective in vivo in combination with CDV than when used alone, but this was not observed in our animal study. Mitoxantrone has demonstrated several immunomodulatory activities in addition to its anti tumor proliferation activity, including the suppression of B and T cells Candesartan and the promotion of a TH2 type cytokine response. Such immuno modulation can be beneficial for treating autoimmune disorders such as multiple sclerosis. Clearance of poxvirus infections, however, requires both B and T cell activity, and, at least in the case of ectromelia virus, a TH1 cytokine response. It is therefore possible that the immunomodulatory activity was enough to negate any in vivo synergistic activity between MXN and CDV. In agreement with a previous report which found that MXN exhibited no in vivo activity against intranasal VACV infection in BALB/c mice, we observed no efficacy against intranasal CPXV infection in BALB/c mice. Mitoxantrone did, however, demonstrate efficacy when used to treat intraperitoneally infected C57Bl/6 mice, suggesting that differences in the route of infection and in mouse strain susceptibility to infection may influence MXN efficacy. While related anthracenediones have been reported to have in vivo antiviral activity against viruses unrelated to poxviruses, to our knowledge this is the first report of limited in vivo antiviral activity by MX.